Radio frequency (RF) energy can be used to ablate solid tissue, thus inducing localized tissue necrosis. RF energy is particularly useful in this capacity for inducing necrosis in sub-dermal lesions and tumors such as those found in cancers of the liver, stomach, kidney, lung, bowel, pancreas, and breast. The conventional delivery system for this sort of treatment is an electro-surgical probe, and one benefit to using such a probe is that it is much less invasive than a full surgical procedure to remove the pathology. As a consequence, recovery time, morbidity, and mortality are greatly reduced, and costs are lowered.
As radio frequency thermal ablation (RFA) technology has been refined, it has become possible to ablate relatively large tumors using image guided probe placement. The imaging techniques available include computerized axial tomography scanning, magnetic resonance imaging, ultrasound imaging, and laparoscopy.
As RFA and other minimally invasive treatments of localized cancers evolve, support equipment is needed to increase the efficiency and efficacy of the treatment. This is particularly true in the use of RFA for treating breast disorders because of the pliability of the tissue involved. This tissue pliability also complicates the taking of a percutaneous biopsy of a suspected abnormality—an important step in diagnosing breast cancer.
The difficulty arises because when a patient lies supine—i.e., on her (or his) back—the breasts fall back as a result of natural gravitational effects, and are compressed onto the costochondral wall, i.e. onto the rib cage. In the process, the tissue abnormality also falls back and settles closer to the rib cage than when the patient is upright. This natural repositioning of the breast presents at least three significant treatment problems.
First, since the abnormality is in a different location than it was when the patient was upright, it is difficult, without ongoing imaging assistance, to accurately aim the medical instrument—either an ablation probe or a biopsy needle—so that upon insertion it goes directly into the abnormality. This problem is exacerbated by the fact that as the medical instrument is inserted into the tissue, the breast tissue naturally shifts because of the force of insertion due to the breast's pliability. This in turn causes the abnormality to move around during treatment.
Second, and perhaps more significantly, since the abnormality is now closer to the rib cage, there is a serious risk that treatment will damage the neighboring costochondral wall and the surrounding healthy tissue. In addition, since the breast is compressed due to gravity, the abnormality may also be closer to the skin surface. Therefore, the ablation process has the potential to cause dermal blistering.
Third, as alluded to above, it is useful to apply an imaging technique during treatment, while the patient is lying supine. This enables the physician to monitor the progress of the treatment, and thus make suitable adjustments to avoid damaging healthy tissue on the one hand, and to ablate all of the cancerous tissue on the other hand. Imaging techniques typically make use of the fact that tumor tissue is denser than healthy tissue, and the images show this density differential as a visual contrast. However, when the breast is compressed while the patient is lying supine, the healthy tissue has the appearance of being denser than normal, while the cancerous tissue's density remains essentially unchanged. Therefore, the effectiveness of the imaging process in identifying the tumor is compromised, or at the very least reduced, since the sharpness of the visual contrast is decreased.
One approach to obviating these problems is to use a stereotactic table. A stereotactic table is a table—mounted on a hydraulic lift—that has a hole in it. In use, the patient lies prone on the table, with a breast suspended through the hole, and the physician works on the breast underneath the table. The stereotactic table certainly addresses the problems associated with breast compression due to gravity, since gravity is now used to pull the breast away from the chest wall. However, the table has some serious drawbacks that make it a less than optimal solution to the problems described above.
As of December 2002, each table costs approximately $250,000 US. As a consequence of this high price, there are only about 1,500 units in use in the entire United States. In addition, the table is often uncomfortable for the patient who has to lie prone, with the head cocked to the side, sometimes for up to 45 minutes.
There are devices available that are used for immobilizing or stabilizing other tissue in the body in preparation for tissue ablation or biopsy. However, none of these devices is specific to the breast, and they are, in fact, generally unsuitable for breast immobilization. Indeed, most are designed for use in coronary artery bypass surgery.
For example, temporary immobilization of a local area of tissue has become common in coronary artery bypass surgery, to eliminate cardiac arrest and the need for cardiopulmonary bypass during the bypass surgery. In Placement Of Coronary Artery Bypass Graft Without Pump Oxygenator, 19 Annals Thorac. Surg., No. 1, at 1-9 (January 1975), Trapp and Bisarya describe immobilizing the area of the bypass graft by encircling sutures deep enough to incorporate enough muscle to suspend an area of the heart and prevent damage to the coronary artery. More recently, Fanning, et al., in Reoperative Coronary Artery Bypass Grafting Without Cardiopulmonary Bypass, 55 Annals Thorac. Surg., at 486-89 (February 1993), report immobilizing the area of the bypass graft with stabilization sutures.
A local cardiac immobilization surgical device is discussed in U.S. Pat. No. 5,782,746. The device is used to obtain local cardiac immobilization by temporarily attaching a rigid or semi-rigid cardiac immobilizing member to the heart. This is accomplished by utilizing a partial vacuum between the boundaries of the cardiac immobilizing member and the surface of the heart. In addition, a method and apparatus for temporarily immobilizing a local area of tissue is discussed in U.S. Pat. No. 6,364,826. The method and apparatus are used to temporarily immobilize a local area of heart tissue, so that surgery can be performed on a coronary vessel in that area without significant deterioration of the pumping function of the beating heart.
A physician working on the breast of a patient who is lying supine could, of course, simply manually hold the breast up and away from the chest wall. However, although this approach is, admittedly, much cheaper than the prohibitively expensive stereotactic table, it is decidedly unsatisfactory for a couple of reasons.
First, the physician who holds the breast in one hand only has one hand free to perform the procedure. This means that the physician has very limited access to the medical probe controls. An assistant could be called upon to hold the breast, but unless the physician and the assistant are perfectly coordinated with each other, there is the real potential for surgical error, and at the very least, unnecessary damage to healthy tissue. In addition, there is the possibility of injury to the assistant.
Second, manually holding the breast fails to provide uniform stability and immobilization, since the person holding the breast may get tired—especially if the procedure takes a long time to perform. Therefore, the medical device—either an ablating probe or a biopsy needle—may move around inside the patient in an unintended fashion, possibly causing damage to healthy tissue, or insufficiently ablating the cancerous tissue.
Thus, the available technology fails to provide a satisfactory way to immobilize and stabilize a breast so that tissue ablation, or biopsy, or any other treatment to the breast, can be effectively performed.
Consequently, there is a significant need for a device and method for immobilizing and stabilizing a breast in preparation for tumor ablation, or biopsy, or other medical treatment, that causes minimal discomfort to the patient, can be used with appropriate imaging technology so that the treatment can be monitored while it is being performed, and is inexpensive.